Argoland: Unraveling the mysteries of a lost continent

Geologists have long been intrigued by a missing piece of Earth’s history – a lost continent called Argoland. Around 155 million years ago, a 5,000-kilometer chunk broke off of western Australia and began its solitary drift. 

The void that was left behind is marked by a basin deep below the ocean known as the Argo Abyssal Plain. But, where did Argoland actually go?

A new study from Utrecht University reveals that while Argoland might not exist as a singular mass today, it has not vanished entirely.

The journey of Argoland

Scientists have relied on the underwater Argo Abyssal Plain as evidence of Argoland’s past existence. The seabed structure suggests that the detached continent drifted northwestward, potentially towards present-day Southeast Asia. 

But the mystery deepens, as the vast continent-sized footprint of Argoland is conspicuously absent beneath Southeast Asian islands. Instead, these islands sit atop smaller continental fragments, encircled by significantly older oceanic basins.

This led geologists to dive deeper into the fate of Argoland. They found that the lost continent hasn’t completely disappeared – it has simply shattered into fragments.

Earth’s hidden tales

Earth’s crust varies in weight, comprising heavier oceanic sections and lighter continental chunks. Interestingly, these lighter portions might be lurking below sea level, much like Greater Adria, another lost continent. 

Greater Adria’s journey ended when it submerged into the Earth’s mantle, leaving its top layer behind, which later morphed into the mountains of Southern Europe. Argoland, by contrast, left no evidence in the form of folded rocks.

Study significance

Utrecht University geologist Douwe van Hinsbergen emphasized the significance of tracing these continents. 

“If continents can dive into the mantle and disappear entirely, without leaving a geological trace at the Earth’s surface, then we wouldn’t have much of an idea of what the Earth could have looked in the geological past. It would be almost impossible to create reliable reconstructions of former supercontinents and the Earth’s geography in foregone eras,” said van Hinsbergen.

“Those reconstructions are vital for our understanding of processes like the evolution of biodiversity and climate, or for finding raw materials. And at a more fundamental level: for understanding how mountains are formed or for working out the driving forces behind plate tectonics; two phenomena that are closely related.”

Islands of information 

Van Hinsbergen and his colleague Eldert Advokaat were curious about what the geology of Southeast Asia may reveal about Argoland. 

“But we were literally dealing with islands of information, which is why our research took so long. We spent seven years putting the puzzle together,” said Advokaat. 

“The situation in Southeast Asia is very different from places like Africa and South America, where a continent broke neatly into two pieces. Argoland splintered into many different shards. That obstructed our view of the continent’s journey.” 

Fragmented continent 

But then, Advokaat realized that these fragments converged at their current locations simultaneously, painting a once cohesive picture. Today, the remnants of Argoland can be found beneath the jungles of Indonesia and Myanmar.

This fragmentation was characteristic. Argoland was never a single, solid landmass. Instead, it was an ‘Argopelago,’ a collection of microcontinental chunks interspersed with older oceanic basins. This aspect aligns with other known entities like Greater Adria and Zeelandia.

An evolving planet

The investigation by Advokaat and Van Hinsbergen seamlessly links the geological systems between the Himalayas and the Philippines. Their explorations unravel why Argoland fragmented so intensely. 

Around 215 million years ago, the continent underwent rapid fracturing, breaking into slender splinters. This theory was further supported through field studies on islands such as Sumatra, Borneo, and Timor.

The story of Argoland is not one of complete disappearance but of transformation. As the world continues to evolve, this lost continent serves as a compelling reminder of the ever-shifting nature of our planet.

The study is published in the journal Gondwana Research.

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